Fw: JEP 455: Non-enhanced switch statements
Brian Goetz
brian.goetz at oracle.com
Fri Oct 27 14:28:01 UTC 2023
>
> Unfortunately enum is that one case where compatibility dictates that
> we can't be exhaustive, which is a little sad... but I think that's
> the best we can do?
>
What we do for enums is do exhaustiveness checking based on the
compile-time state of the world, and generate a synthetic default clause
that deals with separately-compiled changes. (Same with sealed types.)
This works pretty well, as it lets us type-check a (new) switch like
int wavelengthNm = switch (trafficLightColor) {
case RED -> 700;
case YELLOW -> 580;
case GREEN -> 540;
}
and not require a "silly" default, while offering runtime protection
against novel colors showing up at runtime, and notifying the user at a
subsequent compile if something unexpectedly changed.
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